Synthesis and Properties of Linear, Cyclic, and Cage Compounds Consisting of Benzodisilacyclobutene Units

本项目合成了带状大环环番化合物和苯环上1，2，4，5-位通过二硅烷链相连的线形同系物，并研究了它们的结构、包合物的形成和电子状态。这些化合物是通过benzo[1，2:4，5]bis(1，1，2，2-tetramethyl-1，2-disilacyclobut-3-ene)与钯配合物的歧化反应合成的。X-射线分析表明，环状四聚体具有带状的菱面体结构，空腔直径为7.3Å，但不含溶剂分子。环状五聚体和环状四聚体八氧化二烯在直径分别为11.9Å和10.4Å的空腔中含有苯分子。苯分子以平行于环芳环的方式被包括。虽然苯分子很容易从空气中环状五聚体的相对较大的空腔中逸出，但环状四聚体八氧化物紧紧地抓住苯分子，不会在空气中和减压下释放它。线性三聚体具有由1，2，4，5-四硅基苯单元组成的锯齿状结构，并在由锯齿状结构形成的空间中含有两个四氢呋喃分子。这种包合方式很少见，被认为是双钳型的。随着1，2，4，5-四硅基苯单元数的增加，这些化合物的紫外光谱表现出红移和消光系数的增加。这些结果表明，硅-硅σ-π轨道与苯环上的σ轨道之间的π共轭作用扩展到了整个分子中。

In this project, the belt-shaped large ring cyclophanes and the linear homologs in which the 1,2,4,5-positions of benzene rings are connected by disilane chains were synthesized, and their structures, the formation of inclusion compounds, and the electronic states were investigated.These compounds were synthesized by the metathesis of benzo[1,2:4,5]bis(1,1,2,2-tetramethyl-1,2-disilacyclobut-3-ene) with the palladium complex. The linear dimer to pentamer and the cyclic tetramer and pentamer have been isolated so far.The X-ray analysis showed that the cyclic tetramer has the belt-shaped rhombohedral structure with a cavity of 7.3 Å diameter, but it does not include a solvent molecule. The cyclic pentamer and the cyclic tetramer octaoxide include a benzene molecule in the cavity of 11.9 and 10.4 Å diameter, respectively. The benzene molecule is included in the parallel manner to the cyclophane ring. Although the benzene molecule easily escapes from the relatively large cavity of the cyclic pentamer in the air, the cyclic tetramer octaoxide holds the benzene molecule tightly and does not release it in the air and under reduced pressure. Therefore, benzene can be reversibly or irreversibly included by controlling the cavity size.The linear trimer has the zigzag structure consisting of 1,2,4,5-tetrasilylbenzene units and includes two tetrahydrofuran molecules in the space formed by the zigzag structure. This inclusion way is rare and is regarded as the double-tweezers type.The UV spectra of these compounds show the bathochromic shift and the increment of the extinction coefficient as the number of the 1,2,4,5-tetrasilylbenzene units increases. These results indicate that the σ-π conjugation between the silicon-silicon σ orbitals and the π orbitals of the benzene rings is extended all over the molecules.